Method of removing high density stickies from secondary papermaking fibers

ABSTRACT

A hybrid method for processing papermaking fibers to remove high density stickies typically includes utilizing a multistage array of forward cleaners coupled with a flotation cell which increases overall efficiency of the system. In a preferred embodiment, a first rejects aqueous stream from a first stage bank of centrifugal cleaners is treated in a flotation cell before being fed to a second stage bank of centrifugal cleaners. With the improved technique, the accepts from the first stage bank of centrifugal cleaners may be combined with the accepts from the second stage bank of centrifugal cleaners and fed forward to a thickening device, for example. The technique is also suitably employed for removing stickies from material which has already been screened with a fine screen.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM FOR PRIORITY

[0001] This application is a continuation-in-part application ofco-pending application Ser. No. 09/772,395, filed Jan. 30, 2001, nowU.S. Pat. No. ______, which in turn was based upon ProvisionalApplication Serial No. 60/180,348, filed Feb. 4, 2000. The priority ofthe foregoing applications, both entitled “Hybrid Multistage ForwardCleaner System With Flotation Cell”, is hereby claimed.

TECHNICAL FIELD

[0002] The present invention relates generally to papermaking fiberprocessing and more particularly to a method useful for removingstickies from secondary or recycle paper pulp by incorporating a hybridmultistage forward cleaner system with an integrated flotation cell. Themethod is particularly effective for removing stickies that have alreadypassed through a screening stage.

BACKGROUND

[0003] Processing of papermaking fibers to remove contaminants is wellknown in the art, including the use of forward cleaners and flotationcells. Such technology is used, for example, to treat secondary(recycle) fiber sources for re-use in paper products such as towel andtissue, paperboard, coated writing and printing papers and so forth.Equipment utilized includes screening devices, flotation cells and thelike as may be seen, for example, in U.S. Pat. Nos. 4,272,315 toEspenmiller; 4,983,258 to Maxham; 5,240,621 to Elonen et al.; and5,693,222 to Galvan et al.

[0004] Recycling paper into secondary pulp suitable for re-use in highquality products is a relatively complex, capital intensive undertakingas will be appreciated from U.S. Pat. No. 5,587,048 to Streisel et al.The basic cleaning sequence of the '048 patent is as follows: (1)detrashing—the detrasher contains 6 mm (¼ inch) holes and retains largecontaminants, such as plastic bags, pieces of wood, large staples,pieces of metal and packing tape, detrashing typically takes place at3-5% solids; (2) high-density cleaning—heavy, coarse contaminants, suchas bolts, staples and rocks are removed, high density cleaning typicallytakes place at about 3-4% solids; (3) primary coarse screening—primarycoarse screens contain holes 2-3 mm in size, preferably 2.4 mm, forremoving medium-sized contaminants, such as small fragments of wood,tape and styrofoam, coarse screening at this stage protects fine slottedscreens downstream from being overwhelmed by contaminants that are largerelative to the slot width, and results in improvement in quality andproduction rates, coarse screening typically takes place at about2.5-3.5% solids; (4) secondary coarse screening—the rejects from theprimary coarse screening may be screened again using holes of the samesize, but at a lower consistency, about 1.5-2.5% solids; (5) sandcleaning (centrifugal)—sand cleaning at this stage protects the fineslotted screens downstream from excess wear, waste corrugated paperboardcontains relatively large amounts of sand, cleaning ahead of the screenincreases the cost of the system, and increases the requirements forhydraulic capacity, sand cleaning typically takes place at about 1%solids; (6) screening—fine slotted screens are used with a width of0.008 inch (0.20 mm), rather than 0.012 inch previously used forcorrugated paperboard, the fine screens remove plastic slivers, wax andstickie agglomerates, screening takes place at less than 1% solids,preferably less than 0.9%; (7) Lightweight Cleaning(Gyrocleaning)—lightweight cleaning preferentially removes materialswith a specific gravity below 1.0, such as plastics, waxes and stickies,not heretofore removed, lightweight cleaning is performed at about 0.8%solids.

[0005] It should be appreciated from the '048 patent that existingmethods for handling stickies removal were based on removing lightcontaminants having a density generally less than the fiber beingcleaned. Such methods have been found inadequate when a significantamount of heavy stickies are present.

[0006] The disclosures of the foregoing patents are hereby incorporatedby reference.

SUMMARY OF INVENTION

[0007] In the past there were mainly small light weight stickies thatmanaged to get through screens, and most of these small light weightstickies were subsequently removed by the gyro-cleans. More recently,heavy weight stickies started becoming a problem; presumably becausesome of the new pressure sensitive adhesives tend to form heavy weightstickies. The small heavy weight stickies, which managed to get throughscreens, were also accepted by the gyro-cleans or reverse cleaners, butthey were subsequently rejected with alot of fiber by the forwardcleaners. Since the heavy weight stickies from the forward cleaners arestill hydrophobic, it is possible to selectively remove them with aflotation cell after the hydrophobic particles attach themselves to airbubbles in the flotation cell.

[0008] The heavy weight stickies are difficult to remove by flotation ifthey lose their hydrophobic properties during the deinking process(e.g., due to the addition of dispersing chemicals) or if the flotationcell is operated inefficiently (e.g., at too high a consistency or withinsufficient air bubbles or due to inadequate contact between stickiesand air bubbles).

[0009] One advantage of having the flotation cell on the forward cleanerrejects is that it is possible to keep the consistency low, since only10-30% of the total flow is being treated (the percentage depends onreject flow amount). If all the stock is treated in a flotation cell,the tendency is to raise the consistency from 0.5-0.6% to 1% or higherto keep the size and cost of the equipment down. If the designconsistency is already 1%, the heavy weight stickies removal efficiencybecomes even worse when the consistency rises above 1% due to productionincreases. By installing a flotation cell on the forward cleaner rejectsin an existing process, it is possible to design the hybrid cleanerflotation cell system at 0.5-0.6% consistency and obtain improved heavyweight stickies removal efficiency.

[0010] The present invention generally includes a method of processingsecondary fiber to remove high density stickies which have a densitygenerally greater than the fiber including: (a) processing a fiber feedstream to generate a rejects stream enriched in high density stickiesand (b) treating the rejects stream enriched in high density stickieswith a flotation stage to generate an intermediate flotation purifiedstream with a reduced high density stickies content. Preferably, thefeed stream is initially processed by way of a centrifugal separationtechnique, such as feeding the stream to a bank of hydrocyclones, whichgenerate a rejects stream enriched in high density stickies. The highdensity stickies typically have a characteristic area (that is,projected maximum cross-sectional area) of less than about 0.5 mm², andusually less than about 0.3 mm². The treatment by the flotation stage iseffective to remove at least about 40 percent of the high densitystickies present and, in most cases, at least about 50 percent. The highdensity stickies are believed to be derived from pressure sensitiveadhesives.

[0011] In another aspect of the invention there is provided a method ofthin stock processing secondary fiber to remove high density stickieshaving a density generally greater than the fiber includes the steps of:(a) processing a feed thin stock stream at a consistency of less thanabout 2.5%, preferably less than about 1%, to generate a thin stockaccepts stream and a thin stock rejects stream, the thin stock rejectsstream being enriched in high density stickies; and (b) treating thethin stock rejects stream enriched in high density stickies to generatean intermediate flotation purified stream.

[0012] The present invention provides in still another aspect a hybridsystem for processing papermaking fibers and includes a multistage arrayof forward cleaners coupled with a flotation cell which increasesoverall efficiency of the system. In a typical embodiment, a firstrejects aqueous stream from a first stage bank of centrifugal cleanersis treated in a flotation cell before being fed to a second stage bankof centrifugal cleaners. The accepts stream of the first stage bank ofcentrifugal cleaners is fed forward as is the accepts stream of thesecond stage bank of centrifugal cleaners. Preferably, the two acceptsstreams are combined.

[0013] One advantage of feeding the second accepts stream forward isthat it does not have to be returned to the first bank of cleaners forre-cleaning. This reduces the size of the first bank of cleaners orallows an existing installation to operate at a lower consistency. (Thecleaners operate more efficiently at a low consistency of 0.5% than at0.8 or 1%). Another advantage is that the flotation cell typicallyoperates at greater than 60% efficiency on removing hydrophobiccontaminants from the first cleaner rejects, while another cleaner stageremoves less than 50% of the hydrophobic contaminants. As a result alarge quantity of hydrophobic contaminants are removed in the flotationstage, which makes the remaining cleaner stages work more efficientlywith less good fiber loss.

[0014] As will be appreciated by one of skill in the art, the size andcost of a flotation stage for treating secondary fiber can be reduced byup to 75% if it is installed in centrifugal cleaner system as comparedto a full scale treatment of the stock by flotation. The centrifugalcleaner system modeling indicates a 34% reduction in ink speck area oftotal centrifugal cleaner system accepts by removing ink specks from thefirst stage rejects with 80% efficiency in a flotation stage and thenfeeding the flotation accepts forward after centrifugal cleaning of thesecond stage. (24% reduction if second stage rejects are treated in asimilar manner). The ability to feed the centrifugal cleaner rejectsforward (after the flotation stage and additional centrifugal cleaningin the next stage) reduces the stock consistency in the first stage,thereby improving the efficiency of the first stage. The capacity of thesystem is also increased by feeding the second stage centrifugal cleaneraccepts forward. The other centrifugal cleaner stages can also beoperated more efficiently since more than 50% of the ink in the firststage centrifugal cleaner rejects has been removed in the flotationstage. When the centrifugal cleaner accepts are thickened in a press, alarge amount of ink ends up in the pressate. This ink can also beremoved by using the ink-laden pressate as dilution water for thecentrifugal cleaner rejects going to the flotation stage.

[0015] A conventional centrifugal cleaner system (as shown in FIG. 1)normally consists of several stages, whereby the rejects of eachcentrifugal cleaner stage are diluted for cleaning in the next stage andthe centrifugal cleaner accepts are fed backwards to the feed of theprevious stage. The ink speck removal efficiency of the centrifugalcleaner is usually much less than 50% on toner inks in office wastepaper. As a result the total centrifugal cleaner system ink speckremoval efficiency can drop to 30% or less on a furnish containing alarge proportion of office waste.

[0016] By sending the first or second stage centrifugal cleaner rejectsto a flotation stage (as shown in FIG. 2) it is possible to remove amuch higher percentage of the ink specks in office waste. (It waspossible to obtain 80% removal of ink specks during a pilot plant trialwith a flotation cell operated on second stage centrifugal cleanerrejects.) If the accepts of the flotation cell are cleaned in the nextcentrifugal cleaner stage, the centrifugal cleaner accepts from thatstage can then be fed forward to the thickener. Sending centrifugalcleaner accepts forward reduces the load and improves the efficiency ofthe previous centrifugal cleaner stage.

[0017] The present invention is particularly useful in connection withremoving stickies from a thin stock recycle fiber product stream;likewise, it is believed pitch removal is enhanced. Stickies aregenerally a diverse mixture of polymeric organic materials which canstick on wires, felts or other parts of paper machines, or show on thesheet as “dirt spots” or holes. The sources of stickies may bepressure-sensitive adhesives, hot melts, waxes, latexes, binders forcoatings, wet strength resins, or any of a multitude of additives thatmight be contained in recycled paper. The term “pitch” normally refersto deposits composed of organic compounds which are derived form naturalwood extractives, their salts, coating binders, sizing agents, anddefoaming chemicals existing in the pulp. Although there are somediscrete characteristics, there are common characteristics betweenstickies and pitch, such as hydrophobicity, low surface energy,deformability, tackiness, and the potential to cause problems withdeposition, quality, and efficiency in the process. Indeed, it ispossible with the present invention to reduce stickies by 50%, 80% oreven more by employing a flotation cell in a multistage forward cleanersystem as hereinafter described in detail. The rejects from theflotation stage are so full of ink, ash and stickies that they can berejected without any further treatment.

[0018] As will be appreciated from the discussion which follows, apreferred method of cleaning recycle pulp includes combining the acceptsfrom a first centrifugal stage with the accepts from a secondcentrifugal stage which is fed with the flotation-purified rejects ofthe first stage. The process is particularly effective for removingrelatively heavy weight (small size) hydrophobic stickies that havealready passed through a screening stage. This will increaseproductivity of a paper machine utilizing the pulp and decrease papermachine downtime and converting downtime. Stickies build up on wires orfabrics and cause holes to form in the sheet requiring downtime on thepaper machine to remove them. Stickies also build up on doctor blades inpaper machines and get into the dewatering felt and so forth. Inconverting, they can cause problems such as sheets sticking together.They clog emboss rolls and interfrere with the proper operation of otherrolls, cause holes in the sheet and so on. Solvents are typicallyrequired to remove stickies from equipment and this can lead toenvironmental issues.

[0019] In recent years, stickies removal from recycle fiber has becomemore difficult in many cases. Without intending to be bound by anytheory, it is believed that stickies generated from waste paperincluding pressure-sensitive adhesives become more flexible at typicaloperating temperatures (40° C.) of screens and thus tend to pass througheven fine screens.

[0020] The method of the present invention has been employed in acommercial papermill and found to have a dramatic effect on downtime ofthe mill. Prior to installation and employment of the inventive methodof removing contaminants, the plant typically experienced about 10 hoursof downtime per month due to stickies. After employment of the claimedprocess, the plant has run for eight months without a stoppage due tostickies. In preferred embodiments the present invention is thusdirected to a method of removing stickies from secondary or recyclefiber.

[0021] In one preferred mode of practicing the invention there isprovided a method of processing papermaking fibers with a multistagearray of forward cleaners including a plurality of centrifugal cleanersconfigured to generate accepts streams and rejects streams whichconcentrate hydrophobic contaminants including the steps of: (a) feedinga first aqueous feed stream including papermaking fibers to a firststage bank of centrifugal cleaners of the multistage array; (b)generating a first accepts aqueous stream and a first rejects aqueousstream in the first stage bank of centrifugal cleaners, the firstaqueous rejects stream being enriched in hydrophobic contaminants withrespect to the first aqueous feed stream; (c) supplying the firstrejects aqueous stream to a flotation stage; (d) treating the firstrejects aqueous stream in the flotation stage to remove hydrophobicwaste from the first aqueous rejects stream and produce an intermediateaqueous purified feed stream; (e) feeding the aqueous purifiedintermediate feed stream to a second stage bank of centrifugal cleanersof the multistage array, the second centrifugal cleaner being configuredto generate a second accepts aqueous stream; and (f) combining the firstaccepts aqueous stream with the second accepts aqueous stream to form acombined accepts stream. A further step involves thickening the combinedaccepts stream. Generally, the process is carried out at a consistencyof less than about 1%; typically at from about 0.3% to about 0.9%, andpreferably at from about 0.4% to about 0.7%. The multistage array offorward cleaners comprises at least 3 banks of centrifugal cleaners inone embodiment.

[0022] Hydrophobic contaminants removed from the first aqueous rejectsstream by the flotation stage may include an ink composition, such as atoner ink composition.

[0023] Typically, the hydrophobic contaminants removed from the firstaqueous rejects stream by the flotation stage includes stickies, and mayinclude an ink composition and stickies. The process is also believedunexpectedly effective in removing stickies derived from pressuresensitive adhesives.

[0024] In yet another aspect of the invention, there is provided amethod of thin stock processing of secondary fiber to removecontaminants including the steps of: (a) screening a first aqueousstream including secondary papermaking fibers having a consistency ofless than about 2.5% in a screening device with openings having ascreening dimension of less than about 10 mils to generate a screenedaccepts aqueous stream; (b) feeding the screened accepts aqueous streamto a multistage array of cleaners configured to generate centrifugalcleaner accepts streams and centrifugal cleaner rejects stream whichconcentrate heavy hydrophobic contaminants, the rejects stream of atleast one centrifugal cleaner being fed to another centrifugal cleaner;and (c) processing at least one centrifugal cleaner rejects stream of acentrifugal cleaner of the multistage array with a flotation stage toremove hydrophobic contaminants, the flotation stage thereby generatinga flotation purified stream having a reduced hydrophobic contaminantscontent.

[0025] Unless otherwise indicated, terminology appearing herein is givenits ordinary meaning; %, percent or the like refers, for example, toweight percent and “consistency” refers to weight percent fiber orsolids as that term is used in papermaking. “Mils” refers to thousandthsof an inch. The banks of centrifugal cleaners are typically hydrocyclonetype cleaners.

BRIEF DESCRIPTION OF DRAWINGS

[0026] The invention is described in detail below with reference tonumerous examples and the appended Figures wherein like numbersdesignate similar parts throughout and wherein:

[0027]FIG. 1 is a schematic of a conventional multistage forwardcentrifugal cleaner system wherein each bank of cleaners are designatedby a conical element;

[0028]FIG. 2 is a schematic diagram of a hybrid multistage forwardcleaner/flotation apparatus and process of the present invention,wherein a flotation stage is provided to treat the second stage rejectsstream;

[0029]FIG. 3 is a schematic diagram of a hybrid multistage forwardcleaner/flotation apparatus and process of the present invention whereina flotation stage is provided to treat the first stage rejects stream;

[0030]FIG. 4 is a schematic diagram of a hybrid multistage forwardcleaner/flotation apparatus and process of the present invention whereina flotation stage is provided to treat the first stage rejects and thirdstage accepts;

[0031]FIG. 5 is a schematic diagram illustrating an apparatus andprocess of the present invention wherein the hybrid system has dualforward cleaner banks in series and the rejects stream from both of theforward cleaner banks are provided to a flotation cell;

[0032]FIG. 6 is a side broken away view of a screen containing a slottedbasket; and

[0033]FIG. 7 is a plot of residual ink concentration versus location inthe pulp cleaning system.

DETAILED DESCRIPTION

[0034] The invention is described in detail below for purposes ofillustration and exemplification only. Such explanation of particularembodiments in no way limits the scope of the invention which is definedin the appended claims. Referring to FIG. 1, there is shown aconventional forward cleaner system 10 of the type employed at a papermill, for instance, as part of the cleaning process for processingsecondary pulp into paper products. System 10 has five stages 12, 14,16, 18 and 20 of banks of centrifugal cleaners interconnected in themanner shown. Such connections may include suitable piping, mixingtanks, holding vessels and the like (not shown) as may be convenient foroperating the system. Pulp is fed at low consistency to the system at 22to the first bank of cleaners 12 through inlet 24 and centrifugallytreated in the first stage by a bank of hydrocyclones, for example, suchthat the accepts are fed forward at 26 to a thickener (or anothercleaning device) at 28 whereas the rejects, concentrating the heavy,hydrophobic waste in the system are fed to second stage 14 at 28 forfurther treatment in a second stage made up of a second bank ofcentrifugal cleaners 14. Diluent water is added to the rejects streamfrom the first stage as indicated at 30 in an amount suitable for theparticular system or operating conditions. Stream 28 (first stagerejects) is thus fed to the second stage cleaners whereupon bank 14 ofcleaners generates an accepts stream 32 and a rejects stream 34. Stream32 is a recycled to the feed 22 and makes up a portion of the materialfed to the first stage bank of cleaners 12. The first bank of cleanersmay be made up of 50 or more hydrocyclones depending on capacity andperformance desired. Subsequent stages will each contain fewer cleanersthan the previous stage depending upon the amount of rejects, until thefinal stage contains less than 10 cleaners.

[0035] Stream 34 is again enriched with respect to heavy components(with respect to stream 32) and is fed to the third stage 16 bank ofcleaners for further processing. Diluent water may again be added at 36if so desired to stream 34. Stage 16 generates another accepts stream 38which is fed back to the second stage (stream 28) and another rejectsstream 40 enriched in heavy hydrophobic components.

[0036] In like fashion, stream 40 is fed to the fourth stage 18 bank ofcleaners at 42 where diluent water may again be added. The fourth stagegenerates another accepts stream 44 and another rejects stream 46. Thesestreams have the rejects/accepts characteristics noted above.

[0037] Stream 46 is fed to yet another stage 20 of forward cleaners at48 wherein stream 46 is divided into an accepts stream 50 and a rejectsstream 52 as indicated on the diagram. Accepts stream 50 is recycled tothe fourth stage as shown and rejects stream 52 is discarded or furtherprocessed if so desired. There is thus described a conventional forwardcleaner system utilizing centrifugal cleaners in cascaded/refluxingfashion to concentrate the waste material and purify the pulp which isfed forward at a papermaking process to a thickening device or acleaning device such as screens or a reverse cleaner.

[0038] In accordance with the present invention, a flotation stage isadvantageously integrated into a multistage forward cleaner system toremove hydrophobic material and increase the cleaning efficiency.Flotation utilizes the phenomenon that the minerals which are present inthe ground ore can partially be wetted, i.e., they are hydrophilic,while other parts of the minerals are hydrophobic. Hydrophobic particleshave a clear affinity to air. Accordingly, finely distributed air isintroduced into the solid-water-mixture so that the air will attach tothe hydrophobic particles causing them to rise to the surface of themixture or suspension. The hydrophobic particles, such as valuableminerals or the above-mentioned contaminants present in repulped stocksuspensions, collect as froth at the surface of the suspension and areskimmed off with a suitable means such as a paddle or weir. Thehydrophilic particles of the ore or stock suspension remain in theflotation vat. It is also possible to separate two or more usefulminerals selectively by the flotation method, for example, in theseparation of sulfidic lead/zinc ores. For controlling the surfaceproperties of the minerals small amounts of additives of chemical agentsare introduced such as, for example, foaming agents which will help tostabilize the air bubbles, so-called collecting agents which actuallycause the hydrophobic effect and prepare the mineral particles forattachment to the air bubbles, and floating agents which temporarilyimpart hydrophilic properties to the hydrophobic minerals and laterreturn the hydrophobic properties for selective flotation, as mentionedabove. The latter are generally inorganic compounds, mostly salts, whilethe collectors are mostly synthetic organic compounds, and the foamingagents are oily or soapy chemicals such as fatty acid soap.

[0039] The apparatus of the present invention may utilize a variety ofreadily available components. The centrifugal cleaners, for example, areavailable from Ahlstrom (Noormarkku, Finland) or Celleco (Model 270series) (Lawrenceville, Ga., USA) and are arranged in banks as shown inFIGS. 2-5. The flotation stage, which may be multiple cells, arelikewise readily available from Comer SpA (Vicenza, Italy). ComerCybercel® models FCB1, FCB3 and FCB4 are suitable as discussed furtherherein.

[0040] There is illustrated in FIG. 2 an apparatus 100 and method inaccordance with the present invention. Apparatus 100 operates similarlyto apparatus 10 in FIG. 1. Like parts are given like numbers forpurposes of brevity and only differences noted from the discussionabove. The system 100 of FIG. 2 operates as described in connection withsystem 10 of FIG. 1 and is so numbered in the drawing except that system100 has a flotation stage 75 for treating the rejects stream 34 ofsecond stage cleaner 14. Diluent water may be added at 36 as before, andhereafter, stream 34 is treated in the flotation stage to removehydrophobic material. The accepts from the flotation stage, that ispurified as shown by removing hydrophobic waste from stream 34, is thenfed in stream 34′ to third stage cleaner 16. Instead of refluxing theaccepts from the third stage back to the second stage, the acceptsmaterial is fed forward in a product stream 26′ for downstreamprocessing. The hydrophobic rejects (31′) from flotation stage (75) areremoved from system 100.

[0041] In FIG. 3 there is illustrated another apparatus 200 and methodof the present invention. Here again similar flnctioning parts arenumbered as in FIGS. 1 and 2, the discussion of which is incorporated byreference here. Apparatus 200 of FIG. 3 differs from apparatus 10 ofFIG. 1 in that a flotation stage 75 is added to treat the first stagerejects stream 28 to remove hydrophilic waste to produce an intermediatepurified stream 28′ which is fed to the second stage bank of cleaners14. Bank 14 generates a purified accepts stream 32′ which is fed forwardto the thickening or other device 28 along with stream 26. Thehydrophobic rejects (21′) from flotation stage (75) are removed fromsystem 200.

[0042] In FIGS. 4 and 5 there are illustrated alternate embodiments ofthe present invention. Like components are numbered as in FIGS. 1-3above, the discussion of which is incorporated by reference. In theapparatus 300 of FIG. 4, there is provided a flotation cell 75 whichtreats rejects stream 28 from the first centrifugal cleaning stage alongwith accepts stream 38′ from the third centrifugal cleaning stage.Stream 38′ is combined with rejects stream 28 and fed to the flotationstage where hydrophobic material is removed and an intermediate purifiedstream 28′ is produced. Stream 28′ is fed to the second stage 14 ofcentrifugal cleaners. The accepts stream from stage 14 is fed forward asstream 32″ and combined with stream 26 in thickening device 28. Thehydrophobic rejects (21′) from flotation stage (75) are removed fromsystem 300.

[0043] Apparatus 400 of FIG. 5 resembles apparatus 200 of FIG. 3 exceptthat there is provided a preliminary stage 12′ of centrifugal cleaners,the accepts stream 26″ of which is utilized as the feed to stage 12.Rejects stream 28″ of stage 12′ is combined with rejects stream 28 ofstage 12 and fed to flotation stage 75. Accepts stream 32′ of the secondstage cleaners is fed forward with accepts stream 26 of stage 12. Thehydrophobic rejects (21′) from flotation stage (75) are removed fromsystem 400.

EXAMPLES

[0044] Pilot plant trials showed that flotation cells such as the ComerCybercel® can successfully deink secondary centrifugal cleaner rejects,with better results obtained if the consistency is kept close to 0.6%.Consistency refers to weight percent fiber or associated solids such asash unless the context indicates otherwise. Results on 42% office waste(Grade A) and 100% office waste (Grade B) are shown in Table 1. TABLE 1Pilot Plant Results for Brightness Gain, Dirt + Ash Removal Efficiencyon Grades A and B at Halsey and Results Used in Simulation Models Grade:A B Model Consistency: 0.69% 0.90%    0.62% Brightness Gain: 18.5% 5.3%Dirt Removal: 77-89% 65-87% 80% Ash removal: 63%  64%  64%

[0045] A simulation model was used to calculate the impact of a ComerCybercel® flotation cell to deink forward cleaner rejects on solidsloss, ash removal and on removal efficiency of mid-dirt (>150 microns)from a 1^(st) washer to the deinked pulp (while running grade B at 336tpd at the 1^(st) washer): TABLE 2 Impact of Flotation Cell on SolidsLoss, Ash Loss, and Mid-dirt Removal Efficiency (according to theSimulation Model for 6 different configurations on Grade B) Mid- ExampleSolids loss Ash loss dirt Eff. 1 No Flotation cell  8.9 tpd 0.8 tpd96.1% 2 Flotation cell on 2^(nd)  2.7 tpd 0.9 tpd 97.0% stage Rejects 3Flotation cell on  6.7 tpd 1.9 tpd 97.4% 1^(st) stage Rejects 4 As 3with 50% eff. in  6.7 tpd 1.9 tpd 97.7% 1^(st) stage 5 Flotation cell on1^(st)  8.9 tpd 1.9 tpd 97.7% stage Rejects + 3^(rd) stage accepts, 44%eff. in 1^(st) stage 6 Flotation cell on two 1^(st) 11.8 tpd 2.8 tpd98.5% stages

[0046] The following indicators were used to evaluate the performance ofthe pilot plant:

[0047] feed consistency.

[0048] brightness gain of handsheets from accepts compared to feed.

[0049] Dirt removal efficiency of small dirt (<150 microns), mid-dirt(>150 microns) and large dirt (>200 microns).

[0050] Ash removal efficiency.

[0051] The results in Table 3 below for examples 7-14 (duplicate runs)show that even at 0.90% feed consistency it was possible to obtain 5.3%points brightness gain, 73% mid-dirt removal efficiency and 64% ashremoval on Grade B. Operating the flotation cell at 0.69% consistency onGrade A, it was possible to obtain 8.1% points brightness gain, 79%mid-dirt removal efficiency and 63% ash removal. TABLE 3 Comer PilotPlant Results on 2^(nd) stage Cleaner Rejects Feed Brightness Dirt + AshRemoval % Example Anal. Cons. % Ash % Gain Small Mid Large Ash CommentsGrade B  7 1 0.86 3.3 88 71 64 2 4.4% 5.8 87 74 65 59 Accepts = 90% >200 m.  8 1 0.88 5.4 87 74 67 2 3.9% 4.6 86 69 57 52 Accepts = 99% > 200m.  9 1 0.88 6.3 88 78 74 2 5.9% 5.0 87 73 66 68 10 1 0.98 5.9 89 74 613.8% 5.7 86 69 63 77 Average 0.90 4.5% 5.3 87 73 65 64 Grade A 11 1 0.537.3 — — — 2 15.9% 9.4 92 78 72 Accepts = 95% > 200 m. 12 1 0.83 4.2 8870 60 70 2 17.8% 8.2 87 70 64 Accepts = 90% > 200 m. 13 1 0.70 8.6 89 8892 53 2 16.5% 8.0 89 80 80 Accepts = 74% > 200 m. 14 1 — 8.7 91 85 87 672 23.8% 10.4 89 85 85 Average 0.69 18.5% 8.1 89 79 77 63

[0052] The effect of incorporating a flotation stage in accordance withthe present invention into a multistage forward cleaner system wasevaluated with a computer model with respect to the systems illustratedin FIGS. 1-5. Results are summarized in the tables below. DIP refers todeinked pulp and DRE refers to dirt removal efficiency. TABLE 4 Systemof FIG. 1 - Conventional Multi-Stage Cleaner System Flow Cons. Ash AshDirt >150 Dirt >150 SUMMARY gpm % STPD % STPD ppm/1.2 g m²/day WasherThick Stock 540 10.37 335.7 2.53 8.5 720 3310 DWw 4272 0.03 7.7 7 0.51504 158 Gyro Accept 4812 1.19 343.4 2.63 9.0 738 3468 Gyro Accept 4812119 343.4 2.49 8.55 738 3468 Dil. Water 4741 0.03 8.5 7.00 0.60 1504 176Total In 9553 351.9 9.15 3644 1^(st) Stage Cleaner Accept 9492 0.60343.0 2.43 8.34 596 2798 Total out Accept 9492 343.0 8.34 596 2798 Diff.In-out 60 8.9 0.8 846 5^(th) Stage Cleaner Rejects 60 2.46 8.9 9.04 0.806957 847 Total Rejects 60 8.9 0.8 847 Cleaner to Press DRE: 30.0% DREDil. Water Out 9334 0.03 16.8 Press Out 158.5 35.1 326.2 1.9 6.2 4171863 Press to DIP DRE: 93.3% DRE DIP 28 PROCESS Washer - DIP 96.1% DRE

[0053] TABLE 5 System of FIG. 2 - Multi-Stage Cleaner System withFlotation Cell on 2^(nd) Stage Rejects Flow Cons. Ash Ash Dirt >150Dirt >150 SUMMARY gpm % STPD % STPD ppm/1.2 g m²/day Washer Thick Stock540 10.37 335.7 2.53 8.5 720 3310 DWw 4272 0.03 7.7 0.7 0.1 1504 16 GyroAccept 4812 1.19 343.4 2.49 8.5 708 3326 Gyro Accept 4812 1.19 343.42.49 8.55 708 3327 Dil. Water 5666 0.03 10.2 0.70 0.70 150 21 Total In10478 353.5 8.62 3448 1^(st) Stage Cleaner Accept 9492 0.57 327.0 2.257.34 461 2063 3^(rd) Stage Cleaner Accept 927 0.43 23.8 1.39 0.33 373121 Total out Accept 10419 0.56 350.8 7.68 455 2185 Diff. In-out 58 2.70.9 1164 Comer Rejects 42 0.93 2.3 34.77 0.81 32762 1050 5^(th) StageCleaner Rejects 16 0.36 0.3 32.88 0.11 23680 113 Total Rejects 58 2.70.9 1163 Cleaner to Press DRE: 30.0% DRE Dil. Water Out 10261 0.03 18.5Press Out 158.5 35.1 332.4 1.9 6.3 318 1449 Press to DIP DRE: 93.3% DREDIP 21.3 PROCESS Washer - DIP 97.0% DRE

[0054] TABLE 6 System of FIG. 3 - Multi-Stage Cleaner System withFlotation on 1^(st) Stage Rejects Flow Cons. Ash Ash Dirt >150 Dirt >150SUMMARY gpm % STPD % STPD ppm/1.2 g m²/day Washer Thick Stock 540 10.37335.7 2.53 8.5 720 3310 DWw 4272 0.03 7.7 0.7 0.1 150.4 16 Gyro Accept4812 1.19 343.4 2.49 8.5 708 3326 Gyro Accept 4812 1.19 343.4 2.49 8.55708 3327 Dil. Water 7449 0.03 13.4 0.70 0.09 150 28 Total in 12261 356.88.64 3355 1^(st) Stage Cleaner Accept 9492 0.50 282.9 2.13 6.04 443 17152^(nd) Stage Cleaner Accept 2679 0.42 67.1 1.12 0.75 191 175 Total outAccept 12171 0.48 350.1 6.79 394 1890 Diff. In-out 90 6.7 1.85 1465Comer Rejects 74 1.45 6.4 25.91 1.66 15279 1337 5^(th) Stage CleanerRejects 16 0.28 0.3 69.31 0.19 34056 128 Total Rejects 90 6.7 1.85 1465Cleaner to Press DRE: 30.0% DRE Dil. Water Out 12012 0.03 21.6 Press Out158.5 35.1 328.5 1.9 6.2 276 1241 Press to DIP DRE: 93.3% DRE DIP 18.5PROCESS Washer - DIP 97.4% DRE

[0055] TABLE 7 System of FIG. 4 - Multi-Stage Cleaner System withFlotation on 1^(st) St. Rejects + 3^(rd) St. Accepts Dirt >150 FlowCons. Ash Ash ppm/1.2 g Dirt >150 SUMMARY gpm % STPD % STPD Double-dirtm²/day Washer Thick Stock 546 10.37 339.5 2.51 8.52 1489 6921 DWw 42660.015 3.8 0.7 0.0 300 16 Accept 4812 1.19 343.4 2.49 8.55 1476 6937 GyroAccept 4812 1.19 343.4 2.49 8.55 1476 6937 Dil. Water 7543 0.015 6.80.70 0.05 300 28 Total in 12355 350.1 8.60 6965 1^(st) Stage CleanerAccept 10100 0.46 279.2 2.15 6.01 816 3118 2^(nd) Stage Cleaner Accept2104 0.50 62.9 1.16 6.74 729 3416 Total out Accept 12204 0.47 342.2 1.970.73 346 298 Diff. In-out 151 8.0 1.9 3549 Comer Rejects 143 0.91 7.823.75 1.85 31464 3347 5^(th) Stage Cleaner Rejects 8 0.41 0.2 7.68 0.0272988 202 Total Rejects 151 8.0 1.9 3649 Cleaner to Press DRE: 30.0% DREDil. Water Out 12045 0.015 10.8 Press Out 158.5 35.1 331.3 1.9 6.3 5112316 Double-dirt Press to DIP DRE: 93.3% DRE DIP 34 Double-dirt PROCESSWasher - DIP 97.7% DRE

[0056] TABLE 8 System of FIG. 5 - Multi-Stage Cleaner System withFlotation Cell on both 1^(st) Stage Rejects. Dirt >150 Flow Cons. AshAsh ppm/1.2 g Dirt >150 SUMMARY gpm % STPD % STPD double-dirt m²/dayWasher Thick Stock 546 10.37 339.5 2.51 8.5 1489 6920 DWw 4266 0.015 3.80.7 0.0 300 16 Gyro Accept 4812 1.19 343.3 2.49 8.5 1476 6935 GyroAccept 4812 1.19 343.4 2.49 8.55 1476 6937 Dil. Water 7431 0.015 6.70.70 0.05 300 27 Total in 12243 350.0 8.60 6964 1^(st) Stage Cleaner 2Accept 8417 0.44 223.0 1.89 4.21 523 1596 2^(nd) Stage Cleaner Accept3619 0.53 115.3 136 1.56 388 612 Total out Accept 12036 0.47 338.3 5.77477 2208 12036 0.55 400.0 Diff. In-out 208 11.8 2.8 4756 Comer Rejects192 0.99 11.4 24.65 2.81 28167 4389 5^(th) Stage Cleaner Rejects 16 0.390.4 8.54 0.03 71490 367 Total Rejects 208 11.8 2.8 4756 Cleaner to PressDRE: 30.0% DRE Dil. Water Out 11856 0.015 10.7 0.70 0.1 Press Out 180.035.16 327.6 1.74 5.7 334 1497 379.5 double-dirt Press to DIP DRE: 93.3%DRE DIP 22 double-dirt PROCESS Washer - DIP 98.5% DRE

[0057] The process of the present invention is particularly useful inconnection with thin stock processing of recycle fiber, wherein theaqueous stream has a consistency of less than about 1% during suchprocessing. Thin stock processing is employed in connection withcommercial recycling operations, following pulping, thick stock cleaningand washing prior to thickening and bleaching, for example. In apreferred thin stock process in accordance with the invention, the thinstock is screened in a screening device with a screening dimension ofless than about 10 mils to generate a screened accepts aqueous streamwhich, in turn, is fed to a hybrid sytem such as shown in FIG. 4, forexample. The screening dimension of the screening device is the slotwidth of a slotted screen basket, or could be the hole diameter of analternate screening device.

[0058] Slotted screening devices are preferred and are well known. Thereis shown in FIG. 6 such a slotted screening device 500 provided with afeed port 510, a screen 520 provided with a plurality of elongated slotssuch as slots 530, a rejects outlet 540 as well as an accepts outlet550. A feed stream is fed at 510 while the rejects stream is withdrawnat 540 and the screened accepts aqueous stream 560 exits outlet 550.Accepts stream 560 may then be fed forward to a first stage bank ofcentrifugal cleaners for further dilution and processing as describedabove.

[0059] Slotted screens having a slot width of 8 mils or less may beemployed. In commercial processes, fine slotted screens of 6 mils arefrequently employed.

[0060] A commercial operation utilizing thin stock processing as part ofits secondary fiber processing was operated with a hybrid system asshown and described in connection with FIG. 4 above. The multistagearray of forward cleaners was fed with thin stock which had beenscreened with 6 mil slotted screens prior to being fed to the forwardcleaners. The particular arrangement included in sequence fine slottedscreens, gyrocleans followed by the forward cleaner/flotation cellsystem. The flotation cell employed was a Comer-Cybercell™ device whichis preferably operated without diffuser plates. The system was installedalong with expansion of a disk thickener downstream of thin stockprocessing of the fiber. As a result of this project the cleanersstarted performing better (improved dirt removal efficiency) and thehybrid cleaner-flotation cell removed approximately 80% of the dirt, 63%of the stickies and 53% of the ash in the Comer feed with a brightnessincrease of 2.4% points. Process mid dirt removal efficiency increased2.4% (from 96.9% to 98.3%) when running mixed office waste (“MOW”)recycle fiber at 540 ton per day (tpd) input rate. The paper machineshave run without stickies problems for 8 months since the Comer cellcame on line.

[0061] The new treatment protocol operated well on a firnish containing100% mixed office waste (MOW) as shown in Table 9, which compares middirt removal efficiency (MDRE)>0.02−0.5 mm² before and after Comerflotation cell start-up: TABLE 9 Mid Dirt Removal Efficiency Before andAfter Start-up of Hybrid Cleaner - Comer Flotation Cell on a FurnishContaining 100% Mixed Office Waste (MOW) Mid Dirt Removal Efficiency ofDirt > 0.02-0.5 mm² Time Comer- Dis- Disperger - Period Process CleanerCleaner Thickener perger DIP Before 96.4% 45% 53% - 21% 74% 70% Hybridclnr After 97.7% 50% 79% 13% 78% 73% Hybrid

[0062] The Effective Residual Ink Concentration (ERIC) also improvedthroughout the whole deinking system as can be seen in FIG. 7. ERIClevels in the deinked pulp dropped ftom 76 ppm without the inventivethin stock cleaning method to 21 ppm with the hybrid fiber when runningMOW fiber at 365 tpd.

[0063] The performance of the hybrid cleaner—flotation cell issummarized in Table 10. It shows 2.4% points brightness increase, 82%total dirt removal efficiency (TDRE) and 53% ash reduction across thecombination. The quality of the 2^(nd) stage cleaner accepts was evenbetter than the first stage cleaner accepts. TABLE 10 Hybrid Cleaner -Flotation Cell Results Operating On 1^(st) Stage Cleaner Rejects UnitFeed Brightness Dirt Removal Efficiency Ash Operation Cons Ash Br. GainSmall MDRE TDRE Removal Comer 0.65% 2.0% 70.9% 2.0% pts 78.8% 64.3%71.0% 50% St. 2 Cleaner 0.58% 1.0% 72.9% 0.4% pts 47.2% 51.2% 49.7% 10%Accepts Comer-clnr 0.49% 0.9% 73.3% 2.4% pts 85.3% 79.1% 82.0% 53%

[0064] In the plant, the number of stickies in the deinked pulp arecounted 3 times per shift by screening a 150 gram sample of deinked pulpon a flat screen with 0.006 inch slots. The count for MOW based fiberaveraged 3.3 stickies per 150 grams before installation of the hybridsystem and improved to 1.3 stickies per 150 grams after implementationof the process.

[0065] The area of stickies retained on a Pulmac® screen with 4 milslots was also measured for selected samples. The uncompressed stickiesare then counted using a microscope equipped with a grid to estimate thesize of the stickies. Two sets of samples were obtained at 4 locationsin the overall pulp-cleaning process at a first date, prior toinstallation and operation of the hybrid cleaner system (Data Set A), at12 locations at a second date, also prior to installation of the hybridcleaner system (Data Set B) and again at 8 locations in the process at athird date while the hybrid system shown in FIG. 4 was operating (DataSet C). The average results of 20 gram stock samples for each locationare shown in Table 11. The improvement in total stickies removalefficiency from 95.0% to 98.5% is attributed in part to the improvedoperation of the hybrid forward cleaning system over forward cleanersalone. TABLE 11 Comparative Stickies Removal (Small stickies = <0.28mm²; Large stickies = 0.28-1.47 mm²; X-Large stickies = >1.47 mm²)Pulmac Stickies (mm²/100 grams Process Location X- Total Removal andData Set Small Large Large Total Efficiency Data Set A High Density 72219 119 409 Cleaner 1^(st) Washer - out 76.9 51.3 10 138 1^(st)washer-DIP = 85.3% Disperger - in 49.1 0 0 49 Deinked Pulp 20.3 0 0 20HDCL-DIP = 95.0% Data Set B 1^(st) Washer - out 64.0 13.3 0 77 1^(st)washer-DIP = 91.0% Fine Slotted 50.8 3.1 0.54 Screens - out St.1Cleaner - in 42.9 0.5 0 43 St.1 Cleaner - out 36.9 2.8 0 40 St.2Cleaner - out 43.6 0 0 44 Disperger - in 48.9 2.7 0 52 Disperger - out31.9 0 0 32 Deinked Pulp 6.8 0 0 7 Data Set C High Density 102 168 37306 Cleaner 1^(st) Washer - out 54.7 10.9 0 66 1^(st) washer-DIP = 93.0%Fine Slotted 53.1 0 0 53 Screens - out Comer cell - Feed 48.8 0 0 49Comer in-out = 62% Comer Cell - 18.1 0.6 0 19 Accepts Disperger - in35.9 0 0 36 Disp. in-out = 34% Disperger-out 21.6 0 0 22 Deinked Pulp4.6 0 0 5 HDCl-DIP = 98.5%

[0066] It can be seen from Table 11 that the Comer cell was particularlyeffective in removing small stickies, removing over 60 percent of thestickies in the feed to the flotation cell.

[0067] While the invention has been illustrated in connection withnumerous embodiments, modifications to those embodiments within thespirit and scope of the present invention, set forth in the appendedclaims, will be readily apparent to those of skill in the art.

What is claimed is:
 1. A method of processing secondary fiber to removehigh density stickies which have a density generally greater than thefiber which comprises processing a feed stream to generate a rejectsstream enriched in high density stickies and treating the rejects streamenriched in high density stickies with a flotation stage to generate anintermediate flotation purified stream with a reduced high densitystickies content.
 2. The method according to claim 1, wherein the feedstream is processed by way of a centrifugal separation technique togenerate the rejects stream enriched in high density stickies.
 3. Themethod according to claim 2, wherein said feed stream is fed to a bankof hydrocyclones which generate the rejects stream enriched in highdensity stickies.
 4. The method according to claim 1, wherein said highdensity stickies have a characteristic area of less than about 0.5 mm².5. The method according to claim 4, wherein said high density stickieshave a characteristic area of less than about 0.3 mm².
 6. The methodaccording to claim 1, wherein the flotation stage is effective to removeat least about 40 percent of the high density stickies present in therejects stream enriched in high density stickies.
 7. The methodaccording to claim 6, wherein the flotation stage is effective to removeat least about 50 percent of the high density stickies present in therejects stream enriched in high density stickies.
 8. The methodaccording to claim 1, wherein said high density stickies are derivedfrom pressure sensitive adhesives.
 9. A method of thin stock processingsecondary fiber to remove high density stickies having a densitygenerally greater than the fiber comprising: (a) processing a feed thinstock stream at a consistency of less than about 2.5% to generate a thinstock accepts stream and a thin stock rejects stream, said thin stockrejects stream being enriched in high density stickies; and (b) treatingthe thin stock rejects stream enriched in high density stickies in aflotation stage to generate an intermediate flotation purified stream.10. The method according to claim 1, wherein the feed thin stock streamis processed by way of a centrifugal separation technique to generatethe thin stock rejects stream enriched in high density stickies.
 11. Themethod according to claim 10, wherein said feed thin stock stream is fedto a bank of hydrocyclones which generate the thin stock rejects streamenriched in high density stickies.
 12. The method according to claim 11,wherein said feed thin stock stream is processed at a consistency ofless than about 1% to generate the thin stock rejects stream.
 13. Themethod according to claim 12, wherein said feed thin stock stream has aconsistency of from about 0.3% to about 0.9%.
 14. The method accordingto claim 13, wherein said feed thin stock stream has a consistency offrom about 0.4% to about 0.7%.
 15. The method according to claim 12,wherein the stickies are derived from pressure sensitive adhesives. 16.The method according to claim 12, wherein at least about 40 percent ofthe stickies present in said thin stock rejects stream are removed byway of step (b).
 17. The method according to claim 12, wherein at leastabout 50 percent of the stickies present in said thin stock rejectsstream are removed by way of step (b).
 18. The method according to claim12, wherein said high density stickies have a characteristic area ofless than about 0.5 mm².
 19. The method according to claim 18, whereinsaid high density stickies have a characteristic area of less than about0.3 mm².
 20. A method of processing papermaking fibers with a multistagearray of forward cleaners including a plurality of centrifugal cleanersconfigured to generate accepts streams and rejects streams whichconcentrate hydrophoboic contaminants, said method comprising: (a)feeding a first aqueous feed stream including papermaking fibers to afirst stage bank of centrifugal cleaners of said multistage array; (b)generating a first accepts aqueous stream and a first rejects aqueousstream in said first stage bank of centrifugal cleaners, said firstaqueous rejects stream being enriched in heavy hydrophobic contaminantswith respect to said first aqueous feed stream; (c) supplying said firstrejects aqueous stream to a flotation stage; (d) treating said firstrejects aqueous stream in said flotation stage to remove hydrophobicwaste from said first aqueous rejects stream and produce an intermediateaqueous purified feed stream; (e) feeding said aqueous purifiedintermediate feed stream to a second stage bank of centrifugal cleanersof said multistage array, said second centrifugal cleaner beingconfigured to generate a second accepts aqueous stream; and (f)combining said first accepts aqueous stream with said second acceptsaqueous stream to form a combined accepts stream.
 21. The methodaccording to claim 20, further comprising the step of thickening saidcombined accepts stream.
 22. The method according to claim 20, whereinsaid first aqueous feed stream has a consistency of less than about 1%.23. The method according to claim 20, wherein said first aqueous feedstream has a consistency of from about 0.3% to about 0.9%.
 24. Themethod according to claim 23, wherein said first aqueous feed stream hasa consistency of from about 0.4% to about 0.7%.
 25. The method accordingto claim 20, wherein said multistage array of forward cleaners comprisesat least 3 banks of centrifugal cleaners.
 26. The method according toclaim 20, wherein the hydrophobic contaminants removed from said firstaqueous rejects stream by said flotation stage includes an inkcomposition.
 27. The method according to claim 26, wherein said inkcomposition is a toner ink composition.
 28. The method according toclaim 27, wherein the hydrophobic contaminants removed from said firstaqueous rejects stream by said flotation stage comprises an inkcomposition and stickies.
 29. The method according to claim 28, whereinsaid ink composition comprises a toner ink composition and said stickiescomprise stickies derived from pressure sensitive adhesives.
 30. Amethod of thin stock processing of secondary fiber to removecontaminants comprising: (a) screening a first aqueous stream includingsecondary papermaking fibers having a consistency of less than about2.5% in a screening device with openings having a screening dimension ofless than about 10 mils to generate a screened accepts aqueous stream;(b) feeding said screened accepts aqueous stream to a multistage arrayof centrifugal cleaners configured to generate centrifugal cleaneraccepts streams and centrifugal cleaner rejects stream which concentrateheavy streams and centrifugal cleaner rejects stream which concentrateheavy hydrophobic contaminants, the rejects stream of at least onecleaner being fed to another centrifugal cleaner; and (c) processing atleast one centrifugal cleaner rejects stream of a centrifugal cleaner ofsaid multistage array with a flotation stage to remove hydrophobiccontaminants, said flotation stage thereby generating a flotationpurified stream having a reduced hydrophobic contaminants content. 31.The method according to claim 30, wherein said first aqueous stream hasa consistency of from about 0.3% to about 0.9%.
 32. The method accordingto claim 31, wherein said first aqueous stream has a consistency of fromabout 0.4% to about 0.7%.
 33. The method according to claim 30, whereinthe hydrophobic contaminants removed from said first aqueous rejectsstream by said flotation stage includes an ink composition.
 34. Themethod according to claim 30, wherein said ink composition is a tonerink composition.
 35. The method according to claim 30, wherein thehydrophobic contaminants removed from said first aqueous rejects streamby said flotation stage comprises stickies.
 36. The method according toclaim 30, wherein the hydrophobic contaminants removed from said firstaqueous rejects stream by said flotation stage comprises an inkcomposition and stickies.
 37. The method according to claim 36, whereinsaid ink composition comprises a toner ink composition and said stickiescomprise stickies derived from pressure sensitive adhesives.